I don't know if I totally agree. To me whenever I have gotten a nice amplifier be it home or car audio, the amp makes a fairly large impact at lower volumes. Bass just always seems to tighten and music is fuller and more dynamic. Perhaps it is a wattage thing where it is just that instantaneous demand that is supplied without effort compared to a lesser amp or receiver not being able to provide just that nanosecond of high wattage. . .. I don't know but I have noticed the difference at very low volumes on the same setup minus an upgraded amplifier.

Yes, ABX is indeed a wonderful thing. It's staggering the degree to which psychological bias, in the absence of blind comparisons, persuades us to believe we're hearing certain qualities. When ABX protocols (or similar scientific controls) are introduced, these differences evaporate.

That said, there are reasons why some audible differences occur with fairly casual listening comparisons. If you are comparing two receivers, and send the signals through the preamp/tone control sections, the latter will often introduce slight emphasis or de-emphasis right in the midrange, where the boost/cut section of the controls "hinge," which is exactly where our hearing is most acute.

These preamp sections are never perfectly flat, which may explain why some find the H/K units "warmer" than some other brands.

The only true test of the amp sections of receivers or integrated amplifiers would be to use the "amp-in" jacks on both receivers, equalize the playback levels, and then instantaneously switch between them.

Believe me, I used to be a believer (along with an old friend, Kevin Voecks, the designer of Revel Loudspeakers), until I participated in really controlled comparisons of various amplifiers at the NRC in Ottawa. Kevin and I also used to believe there were significant audible differences in CD players (the analog preamp output sections may have errors in frequency that could be audible). After lots of tests that really bruised our egos, we changed our position.

Certainly power output into lower-impedances may introduce audible differences, but so long as the amplifiers (I'm only discussing solid-state designs), are not driven into clipping or near-clipping (distortion rises quickly as an amplfier approaches clipping), distortion is less than 0.5%, and the frequency response measures flat, then well-designed solid-state amplifiers that I've compared do not exhibit audible differences.

I'm surprised preamps can do that: I thought that since it is a relatively mature technology, all the nonlinearities would be worked out by now. Interesting.

Since I've been playing around with the idea of using a pro grade soundcard as the source/preamp(M-Audio Audiophile 2496, etc) for a while now, I'm kind of interested in what kind of effect it'd have vs a seperate preamp. $100 for a source and preamp would be a steal.

Hell, from MY point of view... I was probably the worst of the worst. I remember my grandparents had a friend of the family that built custom speakers (during the wood-panelling party rec room era) build them some pretty impressive stereo speakers. First time I'd ever seen multiple drivers and porting in an enclosure - when I hit 13 and knew everything, I made a crack one day in front of him how some Monster speaker cable would probably make those things sing.

No one gives a dismissive cold stare like an old German craftsman. I thought he was just an a-hole until I got my start in pro audio.

After my grandparents moved into a home, I took them down. The craftsmanship was incredible (they were ply, though - no MDF in those days) - interior bracing throughout, and even with 25-30 year old driver technology, they sounded pretty damned nice.

I should actually save them from storage behind the furnace at my parents' place.